11 James is investigating the amount of time retired people spend each day using social media. He collects a sample by advertising in a local newspaper for people to complete an online survey.
- State
- the name of the sampling technique he is using,
- one disadvantage of using this technique.
James processes his data in order to draw a histogram. His table of results is shown below.
| Time spent using social media in minutes | \(0 -\) | \(15 -\) | \(30 -\) | \(60 -\) | \(120 - 240\) |
| Number of people per minute | 12.2 | 14.0 | 8.4 | 7.3 | 3.1 |
- Show that the size of the sample is 1455 .
- Calculate an estimate of the probability that a retired person spends more than an hour per day using social media.